The present invention relates generally to imaging and radiation treatment apparatus and particularly to such apparatus that employs nanostructures to generate electromagnetic wave energy, such as x-rays.
X-ray imaging and treatment in-situ in body cavities or lumens are known. For example, miniature transducers are known that generate x-rays by direct conversion of laser light (e.g., femtosecond lasers) into x-ray radiation. The miniature transducers may be coupled to flexible insertion devices to permit in-situ radiation treatment within a human body. The flexible insertion device may include optical fibers and/or electrical conductors to supply electrical and/or optical signals to the miniature energy transducer. The miniature energy transducer may include a cathode structure and anode structure spaced apart within a transducer body; and the cathode, anode, and transducer body form a sealed cavity. Electrons may be accelerated from the cathode structure to the anode structure and are stopped by the anode to generate x-rays by the application of electrical pulses.
U.S. Pat. No. 6,148,061 to Shefer et al., issued Nov. 14, 2000, describes a miniature x-ray unit that may be insertable in a body lumen. The x-ray unit includes a first electrical node, a second electrical node and an insulating material. The first and second nodes are separated by a vacuum gap. The first node includes a base portion and a projecting portion, wherein the projecting portion and the second node are surrounded by an x-ray transmissive window through which x-rays exit the unit. The insulating material coaxially surrounds the base portion of the first node such that the insulating material is recessed from the vacuum gap, and the insulator does not extend into the vacuum gap. Recessing the insulating material from the vacuum gap may decrease the likelihood that the insulator will electrically break down due to the accumulation of electrical charge, and/or the accumulation of other materials on the surface of the insulator. On of the nodes is the anode and the other node is the cathode. The cathode is preferably a cold gated field emitter array (FEA) which provides an electron current having a magnitude that is sufficient to satisfy the time constraints on x-ray dose delivery. The cathode is located within a miniature vacuum (i.e., evacuated) chamber in close proximity to the anode, which is maintained at a voltage of up to about 50 kV. Electrons impinge on the anode in a geometry which may allow the emitted x-ray flux to escape from the anode through a transmissive x-ray window (e.g., cylindrically shaped) which surrounds the vacuum gap.
However, the U.S. Pat. No. 6,148,061 x-ray unit may have some disadvantages. For example, the source length is limited by the inter-electrode spacing and, therefore, the axial radiation distribution is non-uniform. Moreover, since the cathode is located within a miniature vacuum chamber, the size of the x-ray window and the amount of radiation that may pass therethrough are constrained to a small area near the nose of the x-ray unit.
The present invention seeks to provide an improved apparatus electromagnetic wave energy emitter (or transducer, the terms being used interchangeably throughout the specification and claims) that may be used for in-situ imaging and radiation treatment. In one embodiment of the invention, the emitter may be constructed as a slender probe with annular electrodes, such as one or more generally coaxial and cylindrical pairs of electrodes. One of the electrodes may serve as an anode and the other as a cathode. Each pair of electrodes may be individually energized. The energy may be emitted over a substantial portion of the length of the electrodes, thereby providing a significantly larger energy emission window not found in the prior art.
In one embodiment, the probe may be shaped as a slender needle. In another embodiment, there may be provided a plurality of such needles, which may be generally parallel to each other. In yet another embodiment, the probe and electrodes may have a helical construction for further increasing the possible treatment volume.
The probe may form part of an imaging system, which cooperates with an energy emission detector, such as but not limited to, a film, a scintillating screen, a fluoroscope or a detector array. In accordance with one embodiment of the present invention, the detector may comprise a linear coaxial array constructed as a needle (or helix), which may be inserted generally in parallel to the energy transducer.
The electromagnetic wave energy may be produced by a hot cathode. Alternatively, in accordance with a preferred embodiment of the invention, a cold cathode may be employed comprising nanostructures, such as but not limited to, carbon nanotubes and nanoparticles, which may produce a flux of electrons for generating electromagnetic wave energy, such as x-rays.
There is thus provided in accordance with a preferred embodiment of the present invention an electromagnetic wave energy emitter including a generally cylindrical probe including generally coaxial first and second electrodes, each of the electrodes having an at least partially cylindrical shape, one of the electrodes being energizable to emit electrons and the other of the electrodes being adapted to receive the electrons and generate electromagnetic wave energy. A grid element may be placed between the first and second electrodes. A controller may be in communication with the grid element, adapted to control a potential of the grid element. The grid element may have an at least partially cylindrical shape. The grid element may be placed concentrically or non-concentrically with respect to the first and second electrodes.
In accordance with a preferred embodiment of the present invention the first electrode includes a generally hollow cylindrical shell and the second electrode is disposed at least partially inside the first electrode.
Further in accordance with a preferred embodiment of the present invention the probe includes a generally hollow cylindrical shell, and the first and second electrodes are disposed and insulatingly spaced apart from one another on the shell.
Still further in accordance with a preferred embodiment of the present invention the first and second electrodes extend generally axially along a longitudinal length of the shell.
In accordance with a preferred embodiment of the present invention a flexible cable is in electrical connection with at least one of the first and second electrodes. In accordance with another preferred embodiment of the present invention the probe is shaped like a needle and may have a sharp nose and a relatively rigid extended or elongate body. Such an embodiment may be used as an x-ray needle.
Further in accordance with a preferred embodiment of the present invention an energy source is provided for energizing at least one of the first and second electrodes.
Still further in accordance with a preferred embodiment of the present invention imaging apparatus is provided that is adapted to form images of structures illuminated by electromagnetic wave energy generated by the emitter. One of the electrodes may serve as the cathode and the other may serve as the anode.
In accordance with a preferred embodiment of the present invention nanostructures are disposed on at least one of the first and second electrodes, the nanostructures being energizable to emit electrons. The nanostructures may include an electron emitting material, or an overcoating of at least one nanolayer of an electron emitting material.
Further in accordance with a preferred embodiment of the present invention the electron emitting material has a surface morphology that is sufficiently nanoscopically rough to provide multiple potential field emission sites.
Still further in accordance with a preferred embodiment of the present invention a plurality of the probes are generally parallel to one other.
In accordance with a preferred embodiment of the present invention the probe has a generally helical construction.
Further in accordance with a preferred embodiment of the present invention the imaging apparatus includes an energy emission detector.
Still further in accordance with a preferred embodiment of the present invention the energy emission detector includes at least one of a film, a scintillating screen, a fluoroscope and a detector array.